And Jimmy Went to the Rainbow's Foot (1971)

The son of an Argentine chemist travels to Vienna to solve the murder of his father. Step by step he realizes that his father was internationally entangled in Secret-Service machinations and chemical-weapon sales, and ends up in mortal danger himself. Meanwhile, he also realizes that there is no connection between his father's murderess and those dubious activities. Her motive for killing him goes back much further, to a court hearing during the Third Reich.